Swab rubber unit for well swab



T. C. WALDROP SWAB RUBBER UNIT FOR WELL SWAB Filed May 4, 1961Elli/Illa" THOMAS C. WALDROP INVENTOR- WQQW A TTOR/VEY Feb. 27, 1962 saa! Wilda/ill m United States This invention relates to a well swabadapted to be lowered in a well pipe or tubing on a wire line and toelevate well fluids in the pipe or tubing upon raising the swab therein,and it concerns more particularly a swab rubber unit for such a swab ashereinafter described.

The swab rubber unit of this invention is an improve ment over the swabrubber units for well swabs of the type generally as shown and describedin Patent No. 2,633,808, April 7, 1953, issued to Jack C. Webber.

The Webber patent above referred to shows, FIGS. 1 to 4, a well swabhaving a swab rubber unit which is molded of resilient material, such asrubber, and has a plurality of longitudinally spaced invertedfrusto-conical, radially outwardly and upwardly inclined flexibleannular rib-like sealing rings or cups formed on a central tubular corewhich, as shown, is bonded directly to a mandrel forming a structuralpart of the swab, but which in practice may be also formed on a separatesleeve receivable on such a mandrel whereby the swab rubber unit,together with the sleeve, is expendable.

An advantageous feature of the swab rubber unit shown in the Webberpatent, as compared to swab rubber units previously employed havinglarge wire reinforced single cups designed to carry the entire load offluids being displaced from a well pipe or tubing, and which arecharacterized by their inflexibility, is that the swab rubber unit shownin the patent, because of its flexibility, is less likely to be damagedupon impact with fixed objects which may obstruct its free movementthrough the well pipe or tubing.

Another advantageous feature of the arrangement shown in the patent isthat the rib-like sealing rings or cups, which are of slightly lessdiameter than the well pipe or tubing but are normally inclined radiallyoutwardly and upwardly, whereby the swab may be readily lowered in awell pipe or tubing, are each designed to resist predetermined pressuredifferentials on opposite sides thereof, so that each carries itsproportionate share of the load of a column of fluid in the well pipe ortubing.

The sealing rings described in the Webber patent are designed to occupy,during various phases of operational loading, all of the followingpositions:

(1) A position at rest in which the sealing rings are not in contactwith the tubing wall,

(2) A position caused by intermediate or optimum loading, in which thesealing rings are deflected downwardly and outwardly to contact thetubing wall and are substantially perpendicular to the tubing wall,

(3) A position caused by loading in excess of the design capacity ef thesealing rings, in which they are flexed downwardly from the position (2)described above.

An object of this invention is to provide an improved swab rubber unithaving incorporated therein all of'the advantages and safety of thearrangement taught by Webber, while at the same time being characterizedby its substantially greater lifting capacity.

This invention contemplates a swab rubber unit in which a series ofradially outwardly extending annular ribs, of smaller diameter than therib-like sealing rings or cups, are formed on the central tubular core,immediately below the sealing rings or cups, respectively, for abutmentagainst the under sides of the sealing rings or cups to resist downwardflexing movement thereof, whereby the sealing rings or cups arereinforced or 4 atent snzaosz Patented Feb- 27, 1962 comprises a metalsleeve having the flexible sealing rings.

or cups molded thereon and having the annular reinforcing or back upribs below the respective sealing rings or cups, which in the form shownare rigid, formed integrally therewith.

This application relates to three other forms of the invention in whichthe central tubular core as well as the flexible sealing rings or cupsand the annular reinforcing or back up ribs below them are of moldedrubber construction, or some other yieldable semi-rigid material.

The invention will be readily understood by referring to the followingdescription and the accompanying drawing, in which:

FIGS. 1 and 2 are elevational views, partly in section taken on a medianline, showing fragmentarily a swab operatively positioned in a well pipeor tubing, the swab including a mandrel having a swab rubber unit of thetype shown in the Webber patent above referred to (FIGS. 1 to 4)received thereon. FIG. 1 shows the flexible sealing rings or cups atrest, while FIG. 2 shows them in' the overloaded position.

FIG. 3 is an elevational view, partly in section taken on a median line,showing a swab operatively positioned in a well pipe or tubing, the swabincluding a mandrel having a swab rubber unit embodying this inventionreceived thereon, and showing the flexible sealing rings or cups, whichare in position to be reinforced or backed up by the annular ribs belowthem, at rest.

FIG. 4 is an elevational view, partly in section taken on a median line,showing fragmentarily the apparatus illustrated in FIG. 3, and showingthe flexible sealing rings or cups in loaded positions.

FIGS. 5 and 6 are elevational views, partly in section t"ken on a medianline, showing fragmentarily a swab operatively positioned in a well pipeor tubing, including another form of swab rubber unit embodying thisinvention. FIG. 5 shows the flexible sealing rings. or cups, which arereinforced or backed up by the annular ribs below them, at rest, whileFIG. 6 shows them in loaded positions. v

FIGS. 7 and 8 are views similar to FIGS. 5 and 6, respectively, showingfragmentarily a swab operatively positioned in a well pipe or tubing,including another form of swab rubber unit embodying this invention.FIG. 7 shows the flexible sealing rings 01 cups, which are reinforced orbacked up by the annular ribs below them, at rest, while FIG. 8 showsthem in loaded positions.

Referring to FIG. 3 of the drawing, the numeral 1 designates generally awell swab which is similar to the swab shown in the Webber patent (FIGS.1 to 4), and which is operatively positioned but under no load in a wellpipe or tubing, indicated by the numeral 2.

The swab 1 includes a tubular mandrel 3 having swab rubber unitsembodying this invention, as hereinafter described, three of which areshown, each designated generally by the numeral 4, received thereon. p

A valve cage 5 having a ball valve 6 therein is secured to the upper endof the mandrel 3, and a wire rope socket 7, shown fragmentarily, issecured to the upper end of the valve cage 5. The ball valve 6, whichserves as a check valve, is adapted to be seated in the upper end of themandrel 3 upon upward movement of the swab 1 in the well pipe or tubing2.

As shown in FIGS. 1 and 2, the mandrel 3 has a swab rubber unit,designated generally by the numeral 8, which corresponds to the swabrubber units 4 shown in FIGS. 3 and 4, received thereon. The swab rubberunit 8 is of the type shown in the Webber patent, as above described,and includes a central tubular core 9 having a plurality oflongitudinally spaced flexible, radially outwardly and upwardly inclinedrib-like sealing rings or cups 11) formed thereon.

In their at rest positions, as shown in FIG. 1, the flexible sealingrings or cups 10 have a diameter slightly less than the diameter of thewell pipe or tubing 2.

i The swab rubber units 4 shown in FIGS. 3 and 4 each include a centraltubular core 11, corresponding to the central tubular core 9 shown inFIGS. 1 and 2, having a plurality of longitudinally spaced flexible,radially outwardly and upwardly inclined rib-like sealing rings or cups12, corresponding to the sealing rings or cups 10 shown in FIGS. 1 and2, formed thereon.

. A series of radially outwardly extending annular ribs 13, of smallerdiameter than the flexible sealing rings or cups 12, are formed on thecentral tubular core 11, immediately below the sealing rings or cups 12,respectively, for abutment upon by the under sides of the sealing ringsor cups 12 when under load to resist further downward flexing movementthereof, whereby the sealing rings or cups 12 are reinforced or backedup by the annular ribs 13 below them and are thereby adapted to liftgreater loads upon upward movement of the swab 1 in the well pipe ortubing 2.

The portions of the flexible sealing rings or cups 12 which extendradially outwardly beyond the support of annular ribs 13, beingrelatively short, are characterized by their relative stiffness wherebythey resist downward flexing.

The central tublar core 11 as well as the flexible sealing rings or cups12 and the annular reinforcing or back up ribs 13 below them, like thecentral tubular core 9 and the flexible sealing rings or cups 10 shownin FIGS. 1 and 2, are formed of resilient or semi-resilient materialsuch as rubber, but the several components may or may not be of the samematerial.

The annular reinforcing or back up rib 13 shown in FIGS. 3 and 4 arebuilt up or thickened on their under sides whereby they resist beingflexed downwardly, and because of their smaller diameter they do notfrictionally engage the well pipe or tubing 2 upon moving the swab 1upwardly therein.

FIGS. and 6 show an arrangement similar to the arrangement shown inFIGS. 3 and 4 in which the annular reinforcing or back up ribs 13, whichare only slightly thicker than the corresponding flexible sealing ringsor cups 12, are characterized by upper faces which are arranged parallelto the under sides of the corresponding flexible sealing rings or cups12, and are separated therefrom only by circumferential slits, so thatwhile the annular reinforcing or back up rigs 13 are adapted to resistdownward flexing of the flexible sealing rings or cups 12, the sealingrings or cups 12 and the annular reinforcing or back up ribs 13 areadapted to be flexed downwardly together upon the application of apredetermined excess pressure differential to opposite sides thereof, asin moving the swab 1 upwardly in the well pipe or tubing 2.

FIGS. 7 and 8 show an arrangement similar to the arrangement shown inFIGS. 5 and 6 in which the annular reinforcing or back up ribs 13 arerelatively thicker and are separated from the under sides of thecorresponding flexible sealing rings or cups 12 by relatively widercircumferential slots.

In all forms shown the back up ribs are smaller in diameter than theinner diameter of the well tubing, while the sealing rings or cups areof substantially the same diameter as the inner diameter of the welltubing. Swab cups embodying this arrangement are characterized bydesirable free movement downward, both through the fluid column and pastprojecting obstructions in the well pipe, since the sealing lips can beeasily flexed upwardly and the back up ribs are recessed relative to theinner well pipe wall. However, on the up-stroke when the cup is underload, the sealing rings flex downwardly into abutment with theirrespective back up ribs, which combination affords a relatively muchgreater resistance to downward flexing, resulting in a larger loadlifting capability.

The invention may be modified in various ways without departing from thespirit and scope thereof.

1 claim:

1. In a swab rubber unit for a well swab, the combination of a centraltubular core having a plurality of longitudinally spaced, flexiblerib-like sealing rings or cups formed thereon and inclined radiallyoutwardly and upwardly therefrom, the flexible sealing rings or cupshaving a diameter in their at rest position corresponding substantiallyto the diameter of a well pipe or tubing, and a series .of radiallyoutwardly extending annular ribs, of smaller diameter than the flexiblesealings rings or cups, formed on the central tubular core, immediatelybelow the sealing rings or cups, respectively, for abutment against theunder sides of the sealing rings or cups to resist downward flexingmovement thereof, whereby the sealing rings or cups are reinforced orbacked up by the annular ribs below them and are thereby adapted to liftgreater loads upon upward movement thereof in the well pipe or tubing.

2. In a swab rubber unit for a Well swab, the combination of a centraltubular core having a plurality of longitudinally spaced, flexiblerib-like sealing rings or cups formed thereon and inclined radiallyoutwardly and upwardly therefrom, the flexible sealings rings or cupshaving a diameter in their at rest positions corresponding substantiallyto the diameter of a well pipe or tubing, and a series of radiallyoutwardly extending annular ribs, of smaller diameter than the well pipeor tubing, formed on the central tubular core, immediately below thesealing rings or cups, respectively, for abutment against the undersides of the sealing rings or cups to resist downward flexing movementthereof, the central tubular core, the flexible sealing rings or cups,and the annular ribs being formed of molded resilient material.

3. The structure of claim 2, the annular ribs being characterized byplanar upper faces which extend radially outwardly from the centraltubular core, perpendicular to 1 its longitudinal axis, and as viewed insectional elevation,

intersect the under sides of the corresponding flexible sealing rings orcups at acute angles, the annular ribs being built up or thickened ontheir under sides whereby they resist being flexed downwardly.

4. The structure of claim 2, the annular ribs being characterized byupper faces which are arranged parallel to the under sides of thecorresponding flexible sealing rings or cups, the "annular ribs having athickness approaching the thickness of the flexible sealing rings orcups, and being closely spaced relative thereto, so that while theannular ribs are adapted to resist downward flexing of the flexiblesealing rings or cups, the sealing rings or cups and the annular ribsare adapted to be flexed downwardly together upon the application of apredetermined pressure differential to opposite sides thereof.

No references cited.

